Marxist Unification Movement (in Catalan: Moviment d'Unificació Marxista) was a political group in Catalonia, Spain. MUM was founded in 1977, during the Spanish transition to democracy, by a group that had left the Socialist Party of National Liberation of the Catalan Countries (PSAN) in 1976 and the Col·lectiu Combat, a splinter-group of the Catalan National Front (FNC).MUM differed from other radical Catalan separatists in its willingness to participate in the Spanish electoral process.